diff options
| -rw-r--r-- | riscv/devices.h | 3 | ||||
| -rw-r--r-- | riscv/ns16550.cc | 10 |
2 files changed, 12 insertions, 1 deletions
diff --git a/riscv/devices.h b/riscv/devices.h index 0030da8..040fe3e 100644 --- a/riscv/devices.h +++ b/riscv/devices.h @@ -148,6 +148,9 @@ class ns16550_t : public abstract_device_t { void update_interrupt(void); uint8_t rx_byte(void); void tx_byte(uint8_t val); + + int backoff_counter; + static const int MAX_BACKOFF = 16; }; class mmio_plugin_device_t : public abstract_device_t { diff --git a/riscv/ns16550.cc b/riscv/ns16550.cc index 7bc1d20..8d7e4de 100644 --- a/riscv/ns16550.cc +++ b/riscv/ns16550.cc @@ -71,7 +71,7 @@ ns16550_t::ns16550_t(class bus_t *bus, abstract_interrupt_controller_t *intctrl, uint32_t interrupt_id, uint32_t reg_shift, uint32_t reg_io_width) - : bus(bus), intctrl(intctrl), interrupt_id(interrupt_id), reg_shift(reg_shift), reg_io_width(reg_io_width) + : bus(bus), intctrl(intctrl), interrupt_id(interrupt_id), reg_shift(reg_shift), reg_io_width(reg_io_width), backoff_counter(0) { ier = 0; iir = UART_IIR_NO_INT; @@ -300,11 +300,19 @@ void ns16550_t::tick(void) return; } + if (backoff_counter > 0 && backoff_counter < MAX_BACKOFF) { + backoff_counter++; + return; + } + int rc = canonical_terminal_t::read(); if (rc < 0) { + backoff_counter = 1; return; } + backoff_counter = 0; + rx_queue.push((uint8_t)rc); lsr |= UART_LSR_DR; update_interrupt(); |